The present invention relates to a route control method in a packet exchange type mobile communication system, and in particular, to a method of redirecting user traffic within an access gateway if users accommodated in a same access gateway or neighboring access gateways communicate with each other.
In a 3.9 generation mobile communication network, represented by LTE (Long Term Evolution) of 3GPP (3rd Generation Partnership Project), all networks are changed to use IP, and therefore, telephone services conventionally provided by circuit switching networks are provided on IP networks.
The IP network of the LTE is comprised of an access network and a service network which is independent on accesses.
The LTE access network is comprised of base stations (eNB) which perform wireless communications, MMEs (Mobility Management Entities) which perform the location control and the connection control for terminals, The SGWs (Serving Gateway) which distribute user traffic to service networks, and PGWs (Packet data network Gateways) which transfers traffic from the SGWs to service networks and collects billing data.
On the other hand, in the case of a telephone service, the access independent service network of the LTE is a call control network referred to as an IMS (IP Multimedia Subsystem). In the IMS, an SIP (Session Initiation Protocol) server called CSCF (Call Session Control Function) performs association of telephone numbers with IP addresses of terminals, and management of call sessions. Moreover, the PGW which connects an LTE access network to the IMS has functions to transfer call control signal from terminals to the CSCF and voice signals between the terminals, and to collect billing data (number of transferred packets, transfer data volume, etc.).
The MME and the SGW of the LTE access network are set up in places near base stations for association with the base stations. In contrast, the PGW which connects between the LTE access network and the IMS is set up at the core network side near the service network for association with the service network. Therefore, in the case where terminals are accommodated in a same SGW in particular, there is a problem in that transfer delay occurs by transferring voice traffic to the PGW for the IMS, and therefore, the bandwidth of the core network is narrowed.
As an example for a method of transferring voice traffic without routing the PGW, there is a “Dual Anchoring Approach” which uses different. IP addresses by distinguishing between the IMS call control communication and the voice communication (for example, refer to an article, “3GPP2 X30-20070514-028R1 MMD Roaming—Dual anchor”). In other words, this method uses IP addresses (Home Address) assigned by the PGW for the IMS for the IMS call control communication, and on the other hand, the IP address assigned by the LTE access network (MME, SGW, or local PGW set up in a place near MME or SGW) is used for voice communication. Thereby, the voice packets route locally in the LTE access network, and therefore, it is possible to reduce the transfer delay.
With respect to other methods, there is a method called “Proxy Mobile IPv6 Route Optimization” which establishes a data path directly between Mobile Access Gateways (equivalent to the SGWs in LTE) which accommodate terminals (for example, refer to an article, “IETF draft-qin-netlmm-pmipro-00 PMIPv6 Route Optimization”). However, the article, “IETF draft-qin-netlmm-pmipro-00 PMIPv6 Route Optimization” describes a method for setting the data path of the Proxy Mobile IPv6 Route Optimization but it does not mention about a trigger Of the setting or a method for determining the subject to be set.